CVE-2026-73252: CWE-191: Integer Underflow (Wrap or Wraparound) in cesanta mongoose
Description
Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TLS stack selected by MG_TLS_BUILTIN in src/tls_builtin.c accepts a TLS 1.3 record whose decrypted size is exactly the 16-byte authentication tag with no plaintext or ContentType byte. In mg_tls_recv_record(), the msgsz length check permits that record and the recv_len calculation underflows to SIZE_MAX, so a later handshake step treats stale buffer contents as a trusted message with an effectively unbounded length. An unauthenticated malicious TLS peer can trigger a heap out-of-bounds read before certificate or Finished validation, causing a remote denial of service. This issue is fixed in version 7.23.
CVSS v3.1
Score 7.5high
Affected software
cesanta
mongoose
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Mongoose versions before 7.23 using the built-in TLS stack (MG_TLS_BUILTIN) improperly handle TLS 1.3 records that contain only the 16-byte authentication tag without any plaintext or ContentType byte. In the function mg_tls_recv_record(), the length check allows such a record, causing the recv_len calculation to underflow to SIZE_MAX. This results in a later handshake step treating stale buffer contents as a trusted message with an effectively unbounded length, which leads to a heap out-of-bounds read. This vulnerability can be triggered by an unauthenticated malicious TLS peer before certificate or Finished validation, causing a remote denial of service. The vulnerability is tracked as CWE-191 (Integer Underflow) and CWE-125 (Out-of-bounds Read).
Potential Impact
An unauthenticated remote attacker can cause a denial of service by triggering a heap out-of-bounds read in the TLS handshake process. There is no impact on confidentiality or integrity, but availability is affected due to the crash or instability caused by the out-of-bounds read.
Mitigation Recommendations
This vulnerability is fixed in mongoose version 7.23. Users should upgrade to version 7.23 or later to remediate this issue. No other mitigation is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-08-11T17:18:01.598Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6acfceae2cdf04f656a1f7e3
Added to database: 10/14/2026, 18:49:18 UTC
Last enriched: 10/14/2026, 19:03:21 UTC
Last updated: 10/14/2026, 19:49:17 UTC
Views: 4
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.