VulnerabilityPublished 13 Nov 2026

CVE-2026-126360: OpenTelemetry Python API · Denial of service through quadratic-time traceparent parsing

Affects opentelemetry-apiSource GCVE Database

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Authoritative record:CVE-2026-126360· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 1.45.2 when convenient.

Data as of 13 Nov 2026, 17:35 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	5.3

Patch: Available – fixed in 1.45.2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade opentelemetry-api to 1.45.2.

Affected software

Product	Affected	Fixed in
PyPIopentelemetry-api	Affected <1.45.2	Fixed in 1.45.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade the opentelemetry-api package to version 1.45.2 or later, which includes a fix that rejects traceparent values longer than 512 characters and removes problematic regex patterns. If upgrading is not immediately possible, implement input validation to reject traceparent values that are oversized or contain embedded carriage return/line feed characters before passing them to the propagator.

Description

The OpenTelemetry Python API's TraceContextTextMapPropagator.extract() method is vulnerable to a regular expression denial of service (ReDoS) attack when processing specially crafted traceparent values. Malicious input containing a trace-context prefix followed by a long whitespace sequence and embedded newlines can cause quadratic-time regex backtracking, leading to excessive CPU consumption and request delays. This vulnerability affects versions prior to 1.45.2. The issue does not allow data disclosure, modification, or code execution but can degrade service availability. The vulnerability is mitigated by upgrading to version 1.45.2 or later, which rejects overly long traceparent values and removes problematic regex patterns.

Impact

The vulnerability results in denial of service through excessive CPU consumption and delayed request processing. It does not lead to data disclosure, data modification, or code execution. Repeated exploitation can sustain service degradation, particularly affecting asynchronous servers that process trace context on event-loop threads.

Summary

CVE-2026-126360 describes a ReDoS vulnerability in the OpenTelemetry Python API's TraceContextTextMapPropagator.extract() function. The flaw arises from processing a malformed traceparent string that includes a trace-context prefix, a long whitespace sequence, and embedded newline characters. This triggers quadratic-time regex backtracking, causing excessive CPU usage and delays in request processing. Exploitation requires attacker-controlled input reaching the propagator via a carrier that preserves embedded newlines and allows large values, such as JSON strings, since HTTP headers disallow embedded newlines. The vulnerability impacts asynchronous event-loop servers by blocking unrelated requests. The fix in version 1.45.2 limits traceparent length to 512 characters and removes overlapping suffix and trailing-whitespace regex expressions. Temporary mitigation includes rejecting oversized or newline-containing traceparent values before extraction.

CWE-1333Inefficient Regular Expression Complexity (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Architecture and Design
Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
System Configuration
Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
Implementation
Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
Regular Expression Exponential Blowup (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 17:35 UTC

WeaknessesCWE-1333

Technical details

References

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