CVE-2026-19566 Affecting libnet-cidr-set-perl package, versions <0.23-1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published12 Aug 2026
- disclosed12 Aug 2026
Introduced: 12 Aug 2026
CVE-2026-19566 (opens in a new tab)How to fix?
Upgrade Debian:unstable libnet-cidr-set-perl to version 0.23-1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream libnet-cidr-set-perl package and not the libnet-cidr-set-perl package as distributed by Debian.
See How to fix? for Debian:unstable relevant fixed versions and status.
Net::CIDR::Set versions before 0.23 for Perl allow memory exhaustion and malformed set ranges via unbounded IPv6 prefix lengths.
The _encode method accepts any prefix length matching (0|[1-9][0-9]*) and passes it to _width2bits(), which builds the mask as '1' x ($width + 8), one character per bit. The _inc() method then unpacks the packed mask into a Perl array of one scalar per byte, so the prefix length alone sets the allocation size: ::/100000000 builds a 100 MB string and a 12.5 million element array. The value being tested is parsed, not just the configured ranges: contains() builds a set from its argument, and _guess_coder() tries the IPv4 coder and then the IPv6 coder, so an IPv4-only set expands an oversized IPv6 prefix length before the mixed address width check rejects it.
Any caller that passes untrusted input to contains() or add() can exhaust process memory. A prefix length above 128 is also stored as a range that does not match the requested block: 2001:db8::/129 stringifies back unchanged, contains() of its own base address returns false, and removing it from a set drops the base address while the set still prints as covering it.
References
- https://security-tracker.debian.org/tracker/CVE-2026-19566
- https://github.com/robrwo/perl-Net-CIDR-Set/commit/e16b27db676fd1ca671fbb31208a22c1b1ba9724.patch
- https://github.com/robrwo/perl-Net-CIDR-Set/security/advisories/GHSA-grjr-r4x5-mx4p
- https://metacpan.org/release/RRWO/Net-CIDR-Set-0.23/changes
- https://www.cve.org/CVERecord?id=CVE-2026-49942