Mongoose: handle_opt() missing opts[1] > len check — 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection
CVSS score
7.5
EPSS probability
%0.3
Risk score
0.0
Published
1 d ago
Etkilenen ürün ve sürüm için yayımlanan güvenlik güncellemesini uygulayın.
Impact on My Inventory
Only the personal products you have added to your account are assessed; an organisation's inventory does not appear here.
Checking session…
Vulnerability description
CVE AI research
DayBreach AI Explanation
Verified against sourcesSources read
1
Source agreement
Tam uyum
Evidence confidence
%55
Short explanation
Mongoose features an out-of-bounds read vulnerability in its built-in TCP/IP stack enabled via MG_ENABLE_TCPIP due to a missing opts[1] length check (S0). An unauthenticated remote peer can corrupt the per-connection TCP MSS value, causing mg_send() calls to transmit truncated payloads (S0). This issue is fixed in version 7.23 according to canonical data (S0).
A remote attacker can disrupt application payload transmissions by corrupting the TCP MSS value, rendering connections unable to send proper data while appearing healthy (S0).
What should be done?
- Upgrade Mongoose to version 7.23 or later (S0)
- Follow the vendor advisory for further updates (S0)
Chain of evidence and sources
Mongoose 7.23 öncesi sürümlerde, handle_opt() fonksiyonu opts[1] > len kontrolünden yoksundur (S0).
Kimlik doğrulaması gerektirmeyen uzak bir eş, bağlantı başına MSS değerini bozabilir (S0).
Show the technical text from the sources
Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TCP/IP stack enabled by MG_ENABLE_TCPIP in src/net_builtin.c does not reject a TCP option whose declared opts[1] length exceeds the remaining option bytes. In handle_opt(), a NOP followed by a truncated MSS option causes opts[3] to be read outside the declared options area and used as the low byte of dmss. An unauthenticated remote peer can corrupt the per-connection MSS value so later mg_send() calls transmit truncated or zero-length application payloads while the TCP connection otherwise appears healthy. This issue is fixed in version 7.23.
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-20, CWE-125
Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.
IMPACT: Affected Products and Software
Affected Products
The following products are affected by CVE-2026-73261 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| 7.5 | CVSS V31 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD |
| 7.5 | CVSS V3_1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CVE CNA |
Patch and Remediation Guide
Solution & Remediation Advisory
1 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.
7.23+ds-1Ubuntu upstream: 7.23+ds-1
Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-73261 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-73261 weaknesses.
Attack Vector and Accessibility
Official Sources and Advisories
Similar Vulnerabilities
Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling
Cesanta Mongoose Out-of-Bounds Read in MG_TLS_BUILTIN ClientHello Session ID Parsing
Mongoose: Path traversal in SSI #include directives enables arbitrary file read
Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
Integer overflow in Cesanta Mongoose
Vulnerability in Ubuntu Openssh
Get this vulnerability through the API
Affected products, version ranges, exploitation status and patch information in a single request, with a free key.
curl -H "x-api-key: $DAYBREACH_API_KEY" \ "https://api.daybreach.dev/api/v1/intel/cves/CVE-2026-73261"