Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. `NumberToDelimitedConverter` uses a lookahead-based regular expression with `gsub!` to insert thousands delimiters. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, the interaction between the repeated lookahead group and `gsub!` can produce quadratic time complexity on long digit strings. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
## Summary
The `parse_options_header()` function in `multipart.py` uses a regular expression with an *ambiguous alternation*, which can cause *exponential backtracking (ReDoS)* when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for **denial of service (DoS)** attacks against web applications using this library to parse request headers or `multipart/form-data` streams.
## Impact
Any WSGI or ASGI application using `multipart.parse_form_data()` directly or indirectly (e.g. while parsing `multipart/form-data` streams) is vulnerable. The slow-down is significant enough to block request handling threads for multiple seconds per request.
## Affected versions
All versions up to and including `1.3.0` are affected. The issue is fixed in `1.2.2`, `1.3.1` and `1.4.0-dev`.
Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Prior to 1.4.26 , t.String({ format: 'url' }) is vulnerable to ReDoS. Repeating a partial url format (protocol and hostname) multiple times cause regex to slow down significantly. This vulnerability is fixed in 1.4.26.
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.5.0-alpha.14 and 8.6.11, a malicious client can subscribe to a LiveQuery with a crafted $regex pattern that causes catastrophic backtracking, blocking the Node.js event loop. This makes the entire Parse Server unresponsive, affecting all clients. Any Parse Server deployment with LiveQuery enabled is affected. The attacker only needs the application ID and JavaScript key, both of which are public in client-side apps. This only affects LiveQuery subscription matching, which evaluates regex in JavaScript on the Node.js event loop. Normal REST and GraphQL queries are not affected because their regex is evaluated by the database engine. This vulnerability is fixed in 9.5.0-alpha.14 and 8.6.11.
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.37.0, cpp-httplib uses std::regex (libstdc++) to parse RFC 5987 encoded filename* values in multipart Content-Disposition headers. The regex engine in libstdc++ implements backtracking via deep recursion, consuming one stack frame per input character. An attacker can send a single HTTP POST request with a crafted filename* parameter that causes uncontrolled stack growth, resulting in a stack overflow (SIGSEGV) that crashes the server process. This issue has been patched in version 0.37.0.
Inefficient Regular Expression Complexity (CWE-1333) in the AI Inference Anonymization Engine in Kibana can lead Denial of Service via Regular Expression Exponential Blowup (CAPEC-492).
minimatch is a minimal matching utility for converting glob expressions into JavaScript RegExp objects. Prior to version 10.2.3, 9.0.7, 8.0.6, 7.4.8, 6.2.2, 5.1.8, 4.2.5, and 3.1.4, nested `*()` extglobs produce regexps with nested unbounded quantifiers (e.g. `(?:(?:a|b)*)*`), which exhibit catastrophic backtracking in V8. With a 12-byte pattern `*(*(*(a|b)))` and an 18-byte non-matching input, `minimatch()` stalls for over 7 seconds. Adding a single nesting level or a few input characters pushes this to minutes. This is the most severe finding: it is triggered by the default `minimatch()` API with no special options, and the minimum viable pattern is only 12 bytes. The same issue affects `+()` extglobs equally. Versions 10.2.3, 9.0.7, 8.0.6, 7.4.8, 6.2.2, 5.1.8, 4.2.5, and 3.1.4 fix the issue.
minimatch is a minimal matching utility for converting glob expressions into JavaScript RegExp objects. Versions 10.2.0 and below are vulnerable to Regular Expression Denial of Service (ReDoS) when a glob pattern contains many consecutive * wildcards followed by a literal character that doesn't appear in the test string. Each * compiles to a separate [^/]*? regex group, and when the match fails, V8's regex engine backtracks exponentially across all possible splits. The time complexity is O(4^N) where N is the number of * characters. With N=15, a single minimatch() call takes ~2 seconds. With N=34, it hangs effectively forever. Any application that passes user-controlled strings to minimatch() as the pattern argument is vulnerable to DoS. This issue has been fixed in version 10.2.1.
ajv (Another JSON Schema Validator) before 8.18.0 is vulnerable to Regular Expression Denial of Service (ReDoS) when the $data option is enabled. The pattern keyword accepts runtime data via JSON Pointer syntax ($data reference), which is passed directly to the JavaScript RegExp() constructor without validation. An attacker can inject a malicious regex pattern (e.g., "^(a|a)*$") combined with crafted input to cause catastrophic backtracking. A 31-character payload causes approximately 44 seconds of CPU blocking, with each additional character doubling execution time. This enables complete denial of service with a single HTTP request against any API using ajv with $data: true for dynamic schema validation. This issue is also fixed in version 6.14.0.
AutoGPT is a platform that allows users to create, deploy, and manage continuous artificial intelligence agents that automate complex workflows. The autogpt before 0.6.32 is vulnerable to Regular Expression Denial of Service due to the use of regex at Code Extraction Block. The two Regex are used containing the corresponding dangerous patterns \s+[\s\S]*? and \s+(.*?). They share a common characteristic — the combination of two adjacent quantifiers that can match the same space character (\s). As a result, an attacker can supply a long sequence of space characters to trigger excessive regex backtracking, potentially leading to a Denial of Service (DoS). This vulnerability is fixed in 0.6.32.
CVE-2026-25547 is a critical denial of service vulnerability in versions of the @isaacs/brace-expansion library prior to 5.0.1. The issue arises from inefficient handling of numeric brace ranges, where repeated ranges cause exponential growth in expansion attempts, leading to excessive CPU and memory consumption. This can crash Node.js processes using the vulnerable library without requiring authentication or user interaction. The vulnerability has a CVSS 4.0 base score of 9.2, indicating critical severity. It affects applications and services that incorporate this library for pattern expansion, particularly in JavaScript/TypeScript environments.
Apollo Server is an open-source, spec-compliant GraphQL server that's compatible with any GraphQL client, including Apollo Client. In versions from 2.0.0 to 3.13.0, 4.2.0 to before 4.13.0, and 5.0.0 to before 5.4.0, the default configuration of startStandaloneServer from @apollo/server/standalone is vulnerable to denial of service (DoS) attacks through specially crafted request bodies with exotic character set encodings. This issue does not affect users that use @apollo/server as a dependency for integration packages, like @as-integrations/express5 or @as-integrations/next, only direct usage of startStandaloneServer.
Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.
Security Fix(es):
* cpython: Python HTMLParser quadratic complexity (CVE-2025-6069)
* python: Quadratic complexity in os.path.expandvars() with user-controlled template (CVE-2025-6075)
* python: cpython: CPython: tarfile extraction filter bypass allows escaping the destination directory (CVE-2026-11940)
* python: Python: CPU Denial of Service in HTML parser via repeated unterminated markup declarations (CVE-2026-15308)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
jsdiff is a JavaScript text differencing implementation. Prior to versions 8.0.3, 5.2.2, 4.0.4, and 3.5.1, attempting to parse a patch whose filename headers contain the line break characters `\r`, `\u2028`, or `\u2029` can cause the `parsePatch` method to enter an infinite loop. It then consumes memory without limit until the process crashes due to running out of memory. Applications are therefore likely to be vulnerable to a denial-of-service attack if they call `parsePatch` with a user-provided patch as input. A large payload is not needed to trigger the vulnerability, so size limits on user input do not provide any protection. Furthermore, some applications may be vulnerable even when calling `parsePatch` on a patch generated by the application itself if the user is nonetheless able to control the filename headers (e.g. by directly providing the filenames of the files to be diffed). The `applyPatch` method is similarly affected if (and only if) called with a string representation of a patch as an argument, since under the hood it parses that string using `parsePatch`. Other methods of the library are unaffected. Finally, a second and lesser interdependent bug - a ReDOS - also exhibits when those same line break characters are present in a patch's *patch* header (also known as its "leading garbage"). A maliciously-crafted patch header of length *n* can take `parsePatch` O(*n*³) time to parse. Versions 8.0.3, 5.2.2, 4.0.4, and 3.5.1 contain a fix. As a workaround, do not attempt to parse patches that contain any of these characters: `\r`, `\u2028`, or `\u2029`.
seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. In versions 0.2.0 through 1.4.0, overriding RegExp serialization with extremely large patterns can exhaust JavaScript runtime memory during deserialization. Additionally, overriding RegExp serialization with patterns that trigger catastrophic backtracking can lead to ReDoS (Regular Expression Denial of Service). This issue has been fixed in version 1.4.1.
CVE-2026-22809 is a Regular Expression Denial of Service (ReDoS) vulnerability found in tarteaucitron.js versions prior to 1.29.0. This vulnerability arises from inefficient regular expression handling of the issuu_id parameter, which can be exploited to cause excessive CPU consumption, leading to denial of service. The vulnerability has a medium severity score of 4.4 and requires local access with high privileges to exploit, without user interaction. It impacts the availability of systems using vulnerable versions of tarteaucitron.js, a popular cookie banner compliance tool. The issue is fixed in version 1.
LangChain versions up to and including 0.3.1 contain a regular expression denial-of-service (ReDoS) vulnerability in the MRKLOutputParser.parse() method (libs/langchain/langchain/agents/mrkl/output_parser.py). The parser applies a backtracking-prone regular expression when extracting tool actions from model output. An attacker who can supply or influence the parsed text (for example via prompt injection in downstream applications that pass LLM output directly into MRKLOutputParser.parse()) can trigger excessive CPU consumption by providing a crafted payload, causing significant parsing delays and a denial-of-service condition.
### Impact
An attacker who exploits this vulnerability can craft a PDF which leads to possibly long runtimes for invalid `startxref` entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected.
### Patches
This has been fixed in [pypdf==6.6.0](https://github.com/py-pdf/pypdf/releases/tag/6.6.0).
### Workarounds
```python
from pypdf import PdfReader, PdfWriter
# Instead of
reader = PdfReader("file.pdf")
# use the strict mode:
reader = PdfReader("file.pdf", strict=True)
# Instead of
writer = PdfWriter(clone_from="file.pdf")
# use an explicit strict reader:
writer = PdfWriter(clone_from=PdfReader("file.pdf", strict=True))
```
### Resources
This issue has been fixed in #3594.
Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path.
CVE-2026-0668 is a medium-severity vulnerability in the Wikimedia Foundation's MediaWiki VisualData Extension version 1.45. It involves inefficient regular expression complexity, leading to a potential Regular Expression Denial of Service (ReDoS) attack. This vulnerability can be exploited remotely without authentication or user interaction, causing service disruption by exhausting server resources. No known exploits are currently reported in the wild. The impact is limited to availability, with no confidentiality or integrity compromise. European organizations running affected MediaWiki versions with the VisualData extension are at risk of service degradation or downtime. Mitigation requires patching or applying workarounds to limit or optimize regex processing. Countries with significant Wikimedia usage and MediaWiki deployments, such as Germany, France, and the UK, are most likely affected. The vulnerability's CVSS score is 5.
