CVE-2026-7790: Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allo

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HIGH 7.5REMOTEUPGRADE

CVE-2026-7790 is a high-severity flaw (CVSS 7.5) affecting cowlib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation. The chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on e

Why this priority

High severity
Remotely exploitable, no login, no user action

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	0.4% (top 63%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-05-11
Last modified	2026-10-26

Publisher (CNA): EEF · Vendor: ninenines

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-11 19:16 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

ninenines cowlib UPGRADE

Affected: >= 0.6.0 and < 2.16.1

Fixed in: 2.16.1

Safe to downgrade to: a release before 0.6.0

1. Check installed version

apt-cache policy cowlib || rpm -q cowlib || cowlib --version

2. UPGRADE to 2.16.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cowlib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cowlib

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 0.6.0 (Debian / Ubuntu)

apt-cache madison cowlib sudo apt install cowlib=<VERSION_BEFORE_0.6.0> sudo apt-mark hold cowlib

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

dnf --showduplicates list cowlib sudo dnf downgrade cowlib-<VERSION_BEFORE_0.6.0> sudo dnf versionlock add cowlib

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.

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-2026-7790?

cowlib: upgrade to 2.16.1. Exact commands for each OS are on this page.

Is CVE-2026-7790 being exploited?

CVE-2026-7790 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-2026-7790 affect?

CVE-2026-7790 affects cowlib. Severity is high (CVSS 7.5). Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation. The chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Ea

How urgent is CVE-2026-7790?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-43969 LOW 3.2 UPGRADE Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP req
CVE-2026-43968 MEDIUM 4.0 UPGRADE Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows SSE even

References

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