8.3

CVE-2026-29035: civetweb Out-of-bounds Write

CVSS: 8.3v4.0HighAwaiting analysis
AliasesUBUNTU-CVE-2026-29035DEBIAN-CVE-2026-29035
Published 11-08-2026Last modified 14-08-2026
Open JSON

Vulnerability summary

CVE-2026-29035 is a high (CVSS 8.3) Out-of-bounds Write vulnerability in civetweb. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48.2% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.3/10
010
High · v4.0 (CVE.org)
EPSS score
0.61%
0%100%
Low · +0.14 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 11-08-2026
    PublishedVulnerability first disclosed.
  2. 14-08-2026
    Last modifiedVulnerability information updated.

Description

CivetWeb (commit 4a4f0c95) contains a heap and stack buffer overflow vulnerability in the read_websocket() function that allows unauthenticated remote attackers to corrupt memory by sending compressed WebSocket frames when both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES are defined. Attackers can negotiate permessage-deflate during the WebSocket handshake and send a crafted frame with the RSV1 bit set, causing the server to write a 4-byte zlib sync trailer out-of-bounds past the allocated buffer, leading to heap metadata corruption, denial of service, or potential code execution.

CVSS metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.61%

Chance of exploitation in the next 30 days

Percentile

48%

Versus all other CVEs

30-day change

+0.14 pp

From 0.47% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.61%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Civetweb1 product
Debian1 product
  • civetwebAll versions (No fix recorded)
Ubuntu1 product
  • civetwebAll versions (No fix recorded)

3 vendors · 3 products

References

5 links