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Fencer Vulns
medium 6.8

CVE-2009-1836 json

Mozilla Firefox before 3.0.11, Thunderbird before 2.0.0.22, and SeaMonkey before 1.1.17 use the HTTP Host header to determine the context o…

published 2009-06-12 17 y ago modified 2026-06-16 4 mo ago also EUVD-2009-1831

cvss
6.8
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.0%
EPSS 2.0% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

Mozilla Firefox before 3.0.11, Thunderbird before 2.0.0.22, and SeaMonkey before 1.1.17 use the HTTP Host header to determine the context of a document provided in a non-200 CONNECT response from a proxy server, which allows man-in-the-middle attackers to execute arbitrary web script by modifying this CONNECT response, aka an "SSL tampering" attack.

Patch / fix

  • thunderbird RHEL 5 PRODUCTIVITY, RHEL 5 2.0.0.22-2.el5_3
  • firefox RHEL 4 3.0.11-4.el4
  • firefox RHEL 5 3.0.11-2.el5_3
  • xulrunner RHEL 5 1.9.0.11-3.el5_3
  • xulrunner-devel-unstable RHEL 5 1.9.0.11-3.el5_3

red hat advisories RHSA-2009:1126RHSA-2009:1095

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2009-1836 updated cvss 1.8

Firefox SSL tampering via non-200 responses to proxy CONNECT requests

  • Red Hat Enterprise Linux (v. 5 server) firefox 3.0.11-2.el5_3, xulrunner 1.9.0.11-3.el5_3, xulrunner-devel-unstable 1.9.0.11-3.el5_3 Red Hat Enterprise Linux AS version 4 firefox 3.0.11-4.el4 Red Hat Enterprise Linux Desktop (v. 5 client) firefox 3.0.11-2.el5_3, xulrunner 1.9.0.11-3.el5_3, thunderbird 2.0.0.22-2.el5_3, xulrunner-devel-unstable 1.9.0.11-3.el5_3 Red Hat Enterprise Linux Desktop version 4 firefox 3.0.11-4.el4 Red Hat Enterprise Linux Desktop Workstation (v. 5 client) xulrunner 1.9.0.11-3.el5_3, xulrunner-devel-unstable 1.9.0.11-3.el5_3 Red Hat Enterprise Linux ES version 4 firefox 3.0.11-4.el4
    fixed: vendor fix RHSA-2009:1095
  • Red Hat Enterprise Linux Optional Productivity Applications (v. 5 server) thunderbird 2.0.0.22-2.el5_3
    fixed: vendor fix RHSA-2009:1126
  • Red Hat Enterprise Linux WS version 4 firefox 3.0.11-4.el4
    fixed: vendor fix RHSA-2009:1095

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.03% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=503578 referenced PoC, tagged "exploit" by a source, unverified
  • bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=479880 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.