Swift Crypto: X-Wing HPKE Decapsulation Accepts Malformed Ciphertext Length

published 2026-04-03 7 mo ago modified 2026-07-24 3 mo ago also EUVD-2026-18570 , GHSA-9m44-rr2w-ppp7

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits: 0; none known

A remote attacker can supply a short X-Wing HPKE encapsulated key and trigger an out-of-bounds read in the C decapsulation path, potentially causing a crash or memory disclosure depending on runtime protections. This issue is fixed in swift-crypto version 4.3.1.

Patch / fix

fixed in 2

swift swift-crypto 4.3.1
Apple macOS 4.3.1

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: partial
Assessed: 7 mo ago (2026-04-03)

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/apple/swift-crypto/security/advisories/GHSA-9m44-rr2w-ppp7 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
swift	swift-crypto	>=4.0.0, <4.3.1	4.3.1

Affected products

Apple macOS

Classification

Weakness

CWE-125 Out-of-bounds Read
CWE-787 Out-of-bounds Write

References

github.com /apple/swift-crypto/security/advisories/GHSA-9m44-rr2w-ppp7
web, exploit, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-28815
advisory
github.com /apple/swift-crypto
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary