Read the docs
TI-2026-74440 Aliases CVE-2026-73252

Heap out-of-bounds read in Mongoose built-in TLS stack

Priority HIGH 72CWE-125Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-125 and the CVSS impact.

Summary

Cesanta Mongoose before 7.23 has a heap out-of-bounds read in its built-in TLS stack. An off-by-one length check in mg_tls_recv_record() lets a TLS 1.3 record holding only the authentication tag wrap a length to an effectively unbounded value (CWE-191). An unauthenticated remote attacker acting as a malicious TLS peer can trigger the read before certificate or Finished validation, causing denial of service.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00376 31st percentileScored 2026-11-07
Fix Fixed mongoose (cesanta): 7.23

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Cesantamongoosebefore 7.237.23Patch availableCNA
  • mongoose VendorCesanta Affected before 7.23 Fixed in 7.23 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*——Cesanta
  • cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:* Versions — — ·Cesanta

Remediation

Upgrade Mongoose to version 7.23 or later, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA mongoose (cesanta) Fixed in 7.23

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-15 Threatist record created from CVE-2026-73252
  2. 2026-10-16 Affected versions changed · Red Hat
  3. 2026-10-16 CVSS score added · Red Hat

References

Other 3

  • TI-2023-23198 Cesanta mjs v2.20.0 was discovered to contain a function pointer hijacking vulnerability… CVSS 3.1CRITICAL 9.8
  • TI-2026-51393 Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling CVSS 3.1CRITICAL 9.1
  • TI-2018-15418 Mongoose Web Server 6.9 Denial of Service via Socket Connection CVSS 4.0HIGH 8.7
  • TI-2026-51389 Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching CVSS 4.0CRITICAL 9.1
  • TI-2023-02723 Cesanta Mongoose MQTT Message Parsing Heap Overflow CVSS 3.1HIGH 8.8
  • TI-2020-15865 Buffer overflow in mg_resolve_from_hosts_file in Mongoose 6.18, when reading from a crafted hosts file. CVSS 3.1HIGH 8.8
See all 154 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences