CVE-2022-37436VulnerabilityPublished 17 Jan 2023Updated 22 Jul 2026

Apache2: Prior to Apache HTTP Server 2.4.55, a malicious backend can cause the response headers to be truncated early, resulting in some headers being

Affects apache2Source GCVE Database

Not known to be exploited · 55% EPSS · CVSS 5.3 Medium · fixed in 2.4.18-2ubuntu3.17+esm9 : patch apache2 as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 55.9% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.4.18-2ubuntu3.17+esm9, 2.4.29-1ubuntu4.26, 2.4.41-4ubuntu3.13 +1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Jan 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Ubuntu 22.04 LTSapache2`pkg:deb/ubuntu/apache2@2.4.52-1ubuntu4.3?arch=source&distro=jammy`Other threats	Affected <2.4.52-1ubuntu4.3	Fixed in 2.4.52-1ubuntu4.3
Ubuntu 20.04 LTSapache2`pkg:deb/ubuntu/apache2@2.4.41-4ubuntu3.13?arch=source&distro=focal`Other threats	Affected <2.4.41-4ubuntu3.13	Fixed in 2.4.41-4ubuntu3.13
Ubuntu 18.04 LTSapache2`pkg:deb/ubuntu/apache2@2.4.29-1ubuntu4.26?arch=source&distro=bionic`Other threats	Affected <2.4.29-1ubuntu4.26	Fixed in 2.4.29-1ubuntu4.26
Ubuntu Pro 16.04 LTSapache2`pkg:deb/ubuntu/apache2@2.4.18-2ubuntu3.17+esm9?arch=source&distro=esm-infra/xenial`Other threats	Affected <2.4.18-2ubuntu3.17+esm9	Fixed in 2.4.18-2ubuntu3.17+esm9
Ubuntu Pro 14.04 LTSapache2`pkg:deb/ubuntu/apache2@2.4.7-1ubuntu4.22+esm15?arch=source&distro=esm-infra-legacy/trusty`Other threats	Affected 2.4.6-2ubuntu2 – 2.4.7-1ubuntu4.22+esm15 38 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Apache HTTP Server version 2.4.55. Users should upgrade to version 2.4.55 or later to remediate this issue. Patch status is confirmed by the version cutoff. Until upgraded, administrators should be aware of the risk posed by malicious backends manipulating response headers.

Description

Prior to Apache HTTP Server 2.4.55, a vulnerability exists where a malicious backend can cause response headers to be truncated early. This truncation results in some headers being included in the response body rather than being processed as headers. Consequently, security-related headers may not be interpreted by the client, potentially weakening security controls.

Impact

The vulnerability impacts the integrity of HTTP response headers by truncating them prematurely, which can cause security headers to be ignored by clients. This may weaken client-side security enforcement that depends on those headers. There is no direct confidentiality or availability impact reported. No known exploits in the wild have been documented.

Summary

Apache HTTP Server versions prior to 2.4.55 are vulnerable to a flaw where a malicious backend can cause early truncation of response headers. This causes some headers to be incorporated into the response body instead of being recognized as headers by the client. If these headers serve security purposes, their omission from the header section can reduce the effectiveness of security mechanisms relying on those headers.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Jul 2026, 00:03 UTC

Technical details

References

Community reviews

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