CVE-2019-9516

CVE-2019-9516 is a medium-severity vulnerability in Apple Swiftnio with a CVSS 3.x base score of 6.5. Its EPSS exploit-prediction score of 56% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-770.

Key facts

Description

Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

Frequently asked questions

What is CVE-2019-9516?
Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.
How severe is CVE-2019-9516?
CVE-2019-9516 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2019-9516 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 56% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-9516?
CVE-2019-9516 primarily affects Apple Swiftnio. In total, 27 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-9516?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-9516 published?
CVE-2019-9516 was published on 2019-08-13 and last updated on 2026-06-17.

References

Affected products (27)

More vulnerabilities in Apple Swiftnio

All CVEs affecting Apple Swiftnio →

Other CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities

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Threat intelligence

Threat-intel indicators referencing this CVE: