CVE-2026-49975: Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of

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HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2026-49975 is a high-severity flaw (CVSS 7.5) affecting http server, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of service via malicious HTTP requests. This issue affects Apache HTTP Server: from 2.4.17 through 2.4.67.

Why this priority

High severity
EPSS top 2%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	33.0% (top 2%)
CISA exploited list	No
Weakness	CWE-789, CWE-409
Published	2026-06-08
Last modified	2026-08-19

Publisher (CNA): Apache Software Foundation · Vendor: apache · debian

Last updated 2026-08-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-08 16:16 UTCPublished CVE record published
2026-08-19 12:18 UTCUpdated Record last modified

apache http server UPGRADE

Affected: >= 2.4.17 and < 2.4.68

Fixed in: 2.4.68

Safe to downgrade to: a release before 2.4.17

1. Check installed version

apt-cache policy http-server || rpm -q http-server || http-server --version

2. UPGRADE to 2.4.68 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade http-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade http-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.4.17 (Debian / Ubuntu)

apt-cache madison http-server sudo apt install http-server=<VERSION_BEFORE_2.4.17> sudo apt-mark hold http-server

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list http-server sudo dnf downgrade http-server-<VERSION_BEFORE_2.4.17> sudo dnf versionlock add http-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · arm-none-eabi-binutils-cs · FIXED · 2.47-1.fc46 · FEDORA-2026-7498616952 · source

sudo dnf upgrade --advisory=FEDORA-2026-7498616952

Debian 12 · apache2 · FIXED · 2.4.67-1~deb12u3

sudo apt update && sudo apt install --only-upgrade apache2 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' apache2)" ge "2.4.67-1~deb12u3" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · apache2 · FIXED · 2.4.67-1~deb13u3

sudo apt update && sudo apt install --only-upgrade apache2 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' apache2)" ge "2.4.67-1~deb13u3" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · mod_http2 · FIXED · mod_http2-2.0.29-4.el10_2.1

sudo dnf upgrade --advisory=RHSA-2026:25225 rpm -q mod_http2

RHEL 10.0 Extended Update Support · mod_http2 · FIXED · mod_http2-2.0.29-2.el10_0.2

sudo dnf upgrade --advisory=RHSA-2026:50538 rpm -q mod_http2

RHEL 9 · mod_http2 · FIXED · mod_http2-2.0.26-6.el9_8.1

sudo dnf upgrade --advisory=RHSA-2026:25057 rpm -q mod_http2

RHEL 9.2 Update Services for SAP Solutions · mod_http2 · FIXED · mod_http2-1.15.19-4.el9_2.8

sudo dnf upgrade --advisory=RHSA-2026:55930 rpm -q mod_http2

RHEL 9.4 Update Services for SAP Solutions · mod_http2 · FIXED · mod_http2-2.0.26-2.el9_4.3

sudo dnf upgrade --advisory=RHSA-2026:55992 rpm -q mod_http2

Alpine 3.21 · apache2 · FIXED · apache2-2.4.68-r0

apk add --upgrade apache2 apk info -v apache2

Alpine 3.21 · nginx · FIXED · nginx-1.26.3-r1

apk add --upgrade nginx apk info -v nginx

Alpine 3.22 · apache2 · FIXED · apache2-2.4.68-r0

apk add --upgrade apache2 apk info -v apache2

Alpine 3.22 · nginx · FIXED · nginx-1.28.3-r3

apk add --upgrade nginx apk info -v nginx

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1859 · source

sudo dnf update --advisory=ALAS2023-2026-1859

Amazon Linux 2 · see advisory · FIXED · ALAS2-2026-3372 · source

sudo yum update --advisory=ALAS2-2026-3372

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: mrx-arafat/CVE-2026-49975-POC (29 stars)
GitHub PoC: EQSTLab/CVE-2026-49975 (14 stars)
GitHub PoC: fevar54/Proof-of-Concept-POC---CVE-2026-49975-HTTP-2-Bomb- (6 stars)

Advisories and coverage

Official advisories

Fortinet PSIRT: HTTP/2 Bomb CVE-2026-49975 2026-08-12
AlmaLinux Errata: [ALSA-2026:25057] Important: mod_http2 security update 2026-06-11

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49975?

http server: upgrade to 2.4.68; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-49975 being exploited?

CVE-2026-49975 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49975 affect?

CVE-2026-49975 affects http server, debian linux. Severity is high (CVSS 7.5). Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of service via malicious HTTP requests. This issue affects Apache HTTP Server: from 2.4.17 through 2.4.67.

How urgent is CVE-2026-49975?

Priority 66/100. High severity; EPSS top 2%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache HTTP Server vulnerabilities · Debian vulnerabilities

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References

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