CVE-2011-3639

MEDIUMCVSS v2 · 4.34.3
EchelonGraph scoreLOW confidence

“—” beside the score: it is equal to NVD's CVSS v2 base score.

This CVE was only ever scored under CVSS v2.0. NVD CVSS v2.0 base 4.3 — NVD rates that MEDIUM (NVD's v2 bands: LOW 0.0–3.9 / MEDIUM 4.0–6.9 / HIGH 7.0–10.0; no CRITICAL band). Vector AV:N/AC:M/Au:N/C:N/I:P/A:N. CVSS v2 is an older, coarser metric than v3.1/v4.0 (no Scope, no User Interaction, no Attack Requirements), so it is not directly comparable to a v3 or v4 score. NVD has never re-scored this record under v3. EPSS predicts 51% exploitation probability in the next 30 days; it does not lift the v2 base. EchelonGraph's fixed weight for EG-KEV Tier 2 (Weaponized) sets EG Risk's exploitation input, not EPSS. Confidence: LOW.

Triggered by: NVD CVSS v2.0 (legacy fallback)
Sources: NVD CVSS v2.0
Weaponized
4.3EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • 95 internet-facing services (distinct ip:port) on record running an affected version — derived from Shodan data (© Shodan); a patched service can stay counted while its port stays open
  • High exploitation likelihood — EPSS 51%
  • Public exploit code is available (Exploit-DB, marked verified by Exploit-DB)
CISA-KEV: Not listedEPSS PROB: 51%CVSS v2: 4.3Exploit: Exploit-DB (verified)Exposed services: 95

A fix is available — apply it.

The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers by using the HTTP/0.9 protocol with a malformed URI containing an initial @ (at sign) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368.

Internet exposure · derived from Shodan data

95 internet-facing services (distinct ip:port) on record running a version that maps to CVE-2011-3639, in our KEV-Exposure radar’s Shodan-derived sample.

across 26 countries (United States, Japan, Canada, Germany, France)top: http_server
See the KEV-Exposure radar →Derived from Shodan data. Shodan data is owned by Shodan, which holds its copyright (© Shodan). EchelonGraph claims no ownership of it or copyright in it. Aggregate, host-redacted.

How it counts: every 12 hours, when Shodan query credits allow, the radar runs one Shodan query per tracked product, reads up to 100 ip:port services per query, and keeps a service when its banner version matches a CISA-KEV or high-EPSS CVE; a service is dropped when neither a search nor a Shodan InternetDB port re-check has refreshed it for 21 days. A re-check that finds the port still listed by Shodan InternetDB refreshes the service without re-reading the banner, so a patched service can stay counted while its port stays open. A count is a banner-version inference over a sample, not an exploit test and not an internet-wide census, and the unit is a service, not a machine: a machine answering on two ports counts twice.

CVSS v2.0 (legacy)
4.3MEDIUMNVD never assigned a CVSS v3 rating to this CVE
EG Score
4.3MEDIUMlow confidence
EG Risk
45
EG Risk 45/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed (value × EchelonGraph’s weight)
Severity43% × 45%
The EG Score, 4.3 of 10.
Exploitation65% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 2 (Weaponized): a constant, not a probability.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
51%
EPSS %ILE
98th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

November 30, 2011

Last Modified

April 29, 2026

References (4)

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhathttpd-0:2.2.3-63.el5_8.12012-02-21redhat
redhathttpd-0:2.2.15-15.el6_2.12012-02-13redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(6 across 6 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
apache2—
  • every version up to 2.2.18-1: fixed in 2.2.18-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
apache2—
  • every version up to 2.2.18-1: fixed in 2.2.18-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
apache2—
  • every version up to 2.2.18-1: fixed in 2.2.18-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
apache2—
  • every version up to 2.2.18-1: fixed in 2.2.18-1
—
Debian:5.0(1)
PackageVulnerable rangeFix by version rangeDependents
apache22.2.9-10+lenny10 ... 2.2.9-10+lenny9 (10 versions)
  • every version up to 2.2.9-10+lenny12: fixed in 2.2.9-10+lenny12
—
Debian:6.0(1)
PackageVulnerable rangeFix by version rangeDependents
apache22.2.16-6 ... 2.2.16-6+squeeze4~bpo50+1 (8 versions)
  • every version up to 2.2.16-6+squeeze6: fixed in 2.2.16-6+squeeze6
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 17× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 78 of 108 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 22 repeat rows among the latest 100 are merged into the row they repeat. The 30 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-12 01:41 UTCEG score recompute
  2. 2026-10-11 13:38 UTCEPSS rescoreEPSS 51% · 98th percentile
  3. 2026-10-10 19:54 UTCEPSS rescoreEPSS 51% · 98th percentile
  4. 2026-10-09 20:00 UTCEPSS rescoreEPSS 51% · 98th percentile
  5. 2026-10-08 16:34 UTCEPSS rescoreEPSS 51% · 98th percentile
  6. 2026-10-07 23:38 UTCEPSS rescoreEPSS 51% · 98th percentile
  7. 2026-10-06 15:10 UTCEPSS rescoreEPSS 51% · 98th percentile
  8. 2026-09-30 22:10 UTCOSV refresh
  9. 2026-09-30 14:58 UTCEPSS rescoreEPSS 51% · 98th percentile
  10. 2026-09-29 08:22 UTCEG score recompute
  11. 2026-09-28 13:44 UTCEPSS rescoreEPSS 51% · 98th percentile
  12. 2026-09-26 15:52 UTCEPSS rescoreEPSS 51% · 98th percentile
  13. 2026-09-24 13:57 UTCEPSS rescoreEPSS 51% · 98th percentile
  14. 2026-09-20 20:08 UTCEPSS rescoreEPSS 51% · 98th percentile
  15. 2026-09-16 13:58 UTCEPSS rescoreEPSS 51% · 98th percentile
  16. 2026-09-15 03:04 UTCEPSS rescoreEPSS 51% · 98th percentile
  17. 2026-09-12 14:54 UTCEPSS rescoreEPSS 51% · 98th percentile
  18. 2026-09-12 03:40 UTCOSV refresh
  19. 2026-09-06 13:41 UTCEPSS rescoreEPSS 51% · 98th percentile
  20. 2026-09-05 15:22 UTCEPSS rescoreEPSS 51% · 98th percentile
  21. 2026-09-04 13:55 UTCEPSS rescoreEPSS 51% · 98th percentile
  22. 2026-08-25 13:43 UTCEPSS rescoreEPSS 51% · 98th percentile
  23. 2026-08-24 08:58 UTCOSV refresh
  24. 2026-08-19 16:58 UTCEPSS rescoreEPSS 51% · 98th percentile
  25. 2026-08-18 13:42 UTCEPSS rescoreEPSS 51% · 98th percentile
Show 53 more
  1. 2026-08-15 01:25 UTCEPSS rescoreEPSS 51% · 98th percentile
  2. 2026-08-08 16:31 UTCEPSS rescoreEPSS 51% · 98th percentile
  3. 2026-08-08 05:49 UTCOSV refresh
  4. 2026-08-06 13:41 UTCEPSS rescoreEPSS 51% · 98th percentile
  5. 2026-08-01 04:10 UTCEPSS rescoreEPSS 51% · 98th percentile
  6. 2026-07-30 01:26 UTCEPSS rescoreEPSS 51% · 98th percentile
  7. 2026-07-26 13:44 UTCEG score recomputeAssessed again: 4.3 MEDIUM
  8. 2026-07-23 01:05 UTCEG score recompute▼ 3.40
  9. 2026-07-23 00:09 UTCEG score recomputeFirst assessed: 3.4 LOW
  10. 2026-07-22 22:24 UTCOSV refresh
  11. 2026-07-22 21:48 UTCEG score recompute
  12. 2026-07-22 14:03 UTCEPSS rescoreEPSS 51% · 98th percentile
  13. 2026-07-21 15:21 UTCEPSS rescoreEPSS 51% · 98th percentile
  14. 2026-07-20 17:03 UTCEPSS rescoreEPSS 51% · 98th percentile
  15. 2026-07-19 02:25 UTCEPSS rescoreEPSS 51% · 98th percentile
  16. 2026-07-18 10:00 UTCEPSS rescoreEPSS 51% · 98th percentile
  17. 2026-07-16 16:58 UTCEPSS rescoreEPSS 51% · 98th percentile
  18. 2026-07-15 16:54 UTCEPSS rescoreEPSS 51% · 98th percentile
  19. 2026-07-15 01:55 UTCEPSS rescoreEPSS 53% · 98th percentile
  20. 2026-07-13 22:25 UTCEPSS rescoreEPSS 53% · 98th percentile
  21. 2026-07-13 06:08 UTCEPSS rescoreEPSS 53% · 98th percentile
  22. 2026-07-11 08:22 UTCEPSS rescoreEPSS 53% · 98th percentile
  23. 2026-07-06 16:23 UTCEPSS rescoreEPSS 53% · 98th percentile
  24. 2026-07-06 02:19 UTCEPSS rescoreEPSS 53% · 98th percentile
  25. 2026-07-05 17:29 UTCOSV refresh
  26. 2026-07-04 06:27 UTCEPSS rescoreEPSS 53% · 98th percentile
  27. 2026-07-02 14:01 UTCEPSS rescoreEPSS 53% · 98th percentile
  28. 2026-07-01 15:02 UTCEPSS rescoreEPSS 53% · 98th percentile
  29. 2026-06-30 23:19 UTCEPSS rescoreEPSS 53% · 98th percentile
  30. 2026-06-28 04:52 UTCEPSS rescoreEPSS 53% · 98th percentile
  31. 2026-06-27 03:05 UTCEPSS rescoreEPSS 53% · 98th percentile
  32. 2026-06-25 13:46 UTCEPSS rescoreEPSS 53% · 98th percentile
  33. 2026-06-23 21:30 UTCEPSS rescoreEPSS 53% · 98th percentile
  34. 2026-06-22 14:22 UTCEPSS rescoreEPSS 53% · 98th percentile
  35. 2026-06-21 01:56 UTCEPSS rescoreEPSS 53% · 98th percentile
  36. 2026-06-18 17:49 UTCEPSS rescoreEPSS 53% · 98th percentile
  37. 2026-06-17 17:49 UTCEPSS rescoreEPSS 53% · 98th percentile
  38. 2026-06-17 04:43 UTCOSV refresh
  39. 2026-06-16 17:49 UTCEPSS rescoreEPSS 53% · 98th percentile
  40. 2026-06-15 17:44 UTCEPSS rescoreEPSS 53% · 98th percentile
  41. 2026-06-13 22:57 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  42. 2026-06-12 23:08 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  43. 2026-06-11 13:56 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  44. 2026-06-10 22:14 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  45. 2026-06-10 13:17 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  46. 2026-06-08 14:14 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  47. 2026-06-07 15:22 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  48. 2026-06-06 13:44 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  49. 2026-06-05 22:44 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  50. 2026-06-05 06:07 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  51. 2026-06-04 13:09 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  52. 2026-06-02 20:10 UTCEPSS rescoreEPSS 9.8% · 93rd percentile
  53. 2026-05-31 22:28 UTCEPSS rescoreEPSS 9.8% · 93rd percentile

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 Exploit-DB entry). Defenders should treat patch urgency accordingly.

  • Exploit-DBEDB-36663✓ verified
    Published Feb 6, 2012

    Apache 2.2.15 mod_proxy - Reverse Proxy Security Bypass

    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(4)

What is CVE-2011-3639?
CVE-2011-3639 is a medium-severity vulnerability; its CVE record was published on November 30, 2011. The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers…
When was CVE-2011-3639 made public?
CVE-2011-3639 was made public on November 15, 2011: that is the date its CVE record's CNA, Red Hat, Inc., gives for when the vulnerability was made public. The CVE record itself was published on November 30, 2011. EchelonGraph's copy of the record carries a last-modified date of April 29, 2026; the record at its source may have been updated since.
Is CVE-2011-3639 actively exploited?
CVE-2011-3639 is not currently on CISA's Known Exploited Vulnerabilities catalog. EchelonGraph's EG-KEV model places it in Tier 2 (Weaponized), which is not evidence of exploitation: Exploit-DB marks a public exploit for it as verified. EchelonGraph does not test whether exploit code works. FIRST EPSS estimates a 51% probability of exploitation in the next 30 days (98th percentile of EPSS-scored CVEs).
How do I remediate CVE-2011-3639?
A fix for CVE-2011-3639 is available: update to the fixed version the vendor names in its advisory.

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