CVE WatchSep 16, 2026

CVE-2026-82720

NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--wit

CVSS

5.9

Medium

EPSS

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KEV

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Exploit Today

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0-100

Published: Sep 16, 2026 · Last modified: Sep 16, 2026 · CWE-416

EPSS · 30d

Not enough EPSS history yet.

Technical description

NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a dropped DoH stream brings down the whole DoH session and does not account properly for other DoH streams in the same session. This leads to use-after-free in those code paths. If the prerequisites are satisfied (possible RPZ drop or heavy client traffic), a malicious actor can trigger the vulnerability with a single DoH connection and the appropriate traffic. Impact is limited as the reads are not user controlled and the use-after-free leads to early returns. However, a hardened allocator can catch the use-after-free and controllably terminate the process resulting to denial of service.

Official references

www.nlnetlabs.nlhttps://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt

Related CVEs

CVECVSSEPSSKEVRExploitTitleMod.

CVE-2026-92627—

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———A heap-use-after-free vulnerability exists in H5T__conv_f_f() in src/H5Tconv.c in HDF5 before 1.14.2. When converting a compound datatype containing floating-point members during a dataset read, a temporary buffer allocated with calloc() is freed and subsequently read from within the same conversion routine. An attacker who can supply a crafted HDF5 file containing a specially constructed compound datatype can trigger the use-after-free when the file is parsed by an application that reads the affected dataset, such as h5dump. This can result in a crash and, depending on heap layout and allocator behavior, may be exploitable for further memory corruption up to remote code execution.4h CVE-2026-196667.5 HIG

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———On a resolver configured to use ``dns64``, if an applicable answer from the authoritative server is malformed in a specific way, the resolver `named` process will exit unexpectedly. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.5h CVE-2026-196625.9 MED

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———An attacker may be able to cause a `named` resolver to abort. The attack requires inducing the victim resolver to send multiple queries for a DNSSEC-signed zone hosted by an authoritative server under the control of the attacker. If the auth responds with a particular sequence of crafted answers, and those answers arrive in a particular order with particular timing, the `named` resolver will encounter a use-after-free bug, and abort. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.6h CVE-2026-782276.5 MED

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———NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray.4h CVE-2026-858938.8 HIG

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———Use after free in Microsoft Edge (Chromium-based) allows an unauthorized attacker to elevate privileges over a network.21h CVE-2026-917499.6 CRI

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———Use after free in Workers in Google Chrome prior to 153.0.8010.47 allowed a remote attacker to potentially execute arbitrary code outside the sandbox via a crafted HTML page. (Chromium security severity: Critical)20h